Please answer this question with caution. And also What if we using Least Recent

Question

Please answer this question with caution. And also What if we using Least Recently Used or Optimal algorithm?

Please give 3 answer and explanation for all 3 cases: First in first out/Least Recently Used/Optimal algorithm. Thanks

Select the best answer. Consider these page references (time is progressing left to right): 1 3 6 1 3 X 6 3 1 The objective is to select the page to replace using First-In First-Out. Assume that when Reference X is made, the main memory for this process contains these pages: 3 6 Select the page to replace. None of these answers 6

Explanation / Answer

Page Replacement Algorithms

Before we go to the question let me explain those three algorithms

Page Fault is loading the page into memory

First In First out : In this the first page came into memory is replaced with the required page.

Page References be                 3 4 5 2 1

Then first three pages are loaded into the memory one by one cause 3 page faults

page memory   has     3(1st) 4(2nd) 5(3rd) pages

then 2 has to be loaded therefore first loaded page will be replaced result 1 page fault

page memory has      2     4      5 pages

then page 1 has to loaded into the memory therefore 4 will be replaced causing 1 page fault.

Page memory has 2 1 5 pages.

Least Recently Used: In this least recently used pages will be replaced .

Let page reference be            3 4 3 5 6 1

Then first three pages are loaded into the memory one by one cause 3 page faults

page memory   has     3(1st) 4(2nd) 5(3rd) pages

then 6 has to be loaded therefore from first least recently used that is page 4 will be replaced resulting 1 page fault

page memory has        3   6      5 pages

then page 1 has to loaded into the memory therefore 5 will be replaced causing 1 page fault.

Page memory has 3 6 1 pages.

Optimal algorithm : I t replaces the page which is not used for longest time.

Let page reference be            3 4 3 5 6 1

Then first three pages are loaded into the memory one by one cause 3 page faults

page memory   has     3(1st) 4(2nd) 5(3rd) pages

then 6 has to be loaded therefore page not used for longest period, that is page 4 will be replaced result 1 page fault

page memory has        3   6      5 pages

then page 1 has to loaded into the memory therefore 5 will be replaced causing 1 page fault.

Page memory has 3 6 1 pages.

Let come to our question

Page references : 1 3 6 1 3 X 6 3 1

Page memory : 3 6 1

Using (FIFO) : first loaded among the three is 3   therefore 3 will be replaced X.

Using Least recently used: least recently used is six therefor 6 will be replaced with X

Using Optimal algorithm: 6 is not used for longest period among them therefore 6 will be replaced.

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